The present invention relates to an IC card having a function to exclude erroneous recording (abnormal or invalid recording) and in particular to a processing method for an IC card system and a structure of the IC card permitting to detect destruction of memory data and prevent an erroneous transaction operation.
As IC cards are utilized more widely for terminal processing devices, etc. in a banking system, in order to carry out correctly various types of processings and raise reliability of the IC cards, various methods are proposed for preventing erroneous transaction operations of the IC cards.
For example, by the method disclosed in JP No. A-59-11478 an attempt is made to supply stably electric power from the exterior by disposing a mechanism transmitting and receiving signals by using light having a wavelength band different from the wavelength band used for the optical electric power supplying mechanism such as a solar cell between a device effecting the processing for an IC card and the IC card in order to increase the freedom of the contact position.
Further, for example, by the method disclosed in JP No. A-59-107491 there is disposed means for outputting voltage information values concerning the write-in voltage necessary for write-in information in a memory element such as a programmable read only memory (EPROM) of the IC card and an external device generates a suitable write-in voltage according to the write-in voltage information in order to prevent erroneous operations such as destruction of the memory data, write-in failure, etc.
Since the principal object of the prior art techniques described above is to supply electric voltage given from the exterior to the IC card, when the power supply from the exterior is interrupted by some external factors or subjected to temporary variations in voltage, e.g. in the middle of the memory writing of the IC card, destruction of the memory data or lowering in the reliability of data due to imperfect updating of the memory may be produced. Furthermore, when undetermined data being held, the memory is connected with an external device, since the external device cannot recognize that the data are undetermined, this gives rise to an erroneous operation. An example of the IC card using electrically erasable programmable read only memory (EEPROM) is disclosed in Nikkei Electronics, Oct. 21, 1985, pp. 127-154, which mentions the function of EEPROM to prevent erroneous write-in operations, but no reference is made therein to prevent logical destruction of transaction data.
Further, if an IC card holding such undetermined data is used as a bankbook or for credit transactions, since the balance is inexact, either it is impossible to defray money to the IC card holder or on the contrary it can happen to defray money more than the real balance. Consequently, the reliability of various transactions in the application fields of IC cards is lowered.